Liquid disengaging system

ABSTRACT

THE EFFICIENCY AND YIELD OF THE GAS COMBUSTION RETORTING PROCESS FOR RECOVERING VALUABLE HYDROCARBONS FROM OIL SHALE IS IMPROVED BY DISENGAGING A MIXTURE OF GAS AND OIL FROM THE DOWNWARDLY MOVING SHALE, SEPARATING THE OIL FROM THE GAS IN A SHALE-FREE AREA AND RETURNING THE   GAS TO THE SHALE BED AT A LEVEL ABOVE THAT AT WHICH SAID MIXTURE WAS DISENGAGED.

Feb. 9, 1971 L JAGEL, JR ET AL 3,562,143

LIQUID DISENGAGING SYSTEM Filed May 27, 1968 2 Sheets-Sheet 1/6(t?0t0ting Chute) /3 (Anti- Segregation Device) i8/Feed Pipes) /9(Off-Gas Headers) I x I /0 i l v I 2 fig v 70p of Disengager 30 i i-132(0/7 Recovery Deck Plate) g n "jl Bottom of Disengager 30 E50(C0n0'uits) .1 v ZSMirD/stributian Ports} 1. 26(Recyc/e 60's HeaderOutlet} I V 1/ lZ/Refractary Bria/r Liner) L v 20 (Diamond Distributor)g FA? v 22(R0// Feeder) jg f- /n|/ent0rs 24 Kenneth J0ge/, Jr

Conveyar) Dal/id L/ederman Lester J Skowrone/ I (Ratary 1i By 4;

Feeder)25\ Age Feb. 9, 1971 AG L, JR" ETAL 3,562,143

LIQUID DISENGAGING SYSTEM 2 Sheets-Sheet 2 Filed May 27, 1968 F/GZ Jam

dm 696M fl 0 0 mJ k m GM M V. I ,0 J m /f m U V AC ,0

m y M n w i w 5 M Q "6 M V 5/\ 5 MW /2V/ 2 6 M 5 United States Patent O13,562,143 Patented Feb. 9, 1971 US. Cl. 208-11 4 Claims ABSTRACT OF THEDISCLOSURE The efficiency and yield of the gas combustion retortingprocess for recovering valuable hydrocarbons from oil shale is improvedby disengaging a mixture of gas and oil from the downwardly movingshale, separating the oil from the gas in a shale-free area andreturning the gas to the shale bed at a level above that at which saidmixture was disengaged.

BACKGROUND OF THE INVENTION The retorting or destructive distillation ofoil shale to recover liquid and gaseous hydrocarbons is fundamentally arelatively simple operation that involves the steps of heating the oilshale to the proper temperature, and recovering the liquid productsevolved. However, the commercial application of this process on a largescale requires a large capital investment in equipment, and the recoveryof useful products is small in comparison with the volume of oil shalethat is retorted.

To effectively handle the large volume of oil shale that is treated in acommercial installation, vertical carbon steel retorts areconventionally employed through which lumps of shale pass by gravity.The energy requirements for the process may be supplied by heating thewalls of the retort. Alternatively, the heat required by the process canbe obtained by combustion of the gaseous products of the distillationwithin the retort under conditions designed to insure maximum transferof heat to the shale and maximum recovery of heat from the gaseous andliquid distillation products and from the solid distillation residue.

Economical and eflicient apparatus for the recovery of valuablehydrocarbons from oil shale is described in US. Pat. No. 2,885,338. Oilshale in particulate form is passed downwardly as a vertical column ofmaterial successively through a preheating zone, a distillation zone, acombustion zone and a residue cooling zone. A solid residue from thecombustion zone is removed in a cool condition at the bottom of thecolumn while the products of combustion and distillation including lowboiling normally liquid products together with noncondensible gasrelatively lean in combustibles are withdrawn above the preheating zonein a relatively cool condition. At least a portion of the noncondensiblegas in a cool condition is recycled to the bottom of the column andpasses upwardly through the downwardly moving residue from thecombustion zone thus cooling the hot residue and itself becoming heatedto a temperature that will support combustion. A combustion supportinggas such as air or oxygen is introduced into the combustion zone andreacts with the combustibles in the system such as the hydrocarboncomponents of the gaseous mixture and the coke contained in the spentshale. The combustion thus initiated generates the required amount ofheat to maintain the entire process in thermal balance. Condensation ofthe shale oil vapors is effected upon contact of the rising hot productsof retortation with the downwardly moving cold shale. A series ofcontiguous hoe trays is positioned within the distillation zone atvarious distances from the center of the column to receive a pluralityof fractions of liquid shale oil condensate of different boiling pointswhich are withdrawn separately through conduits that extend from eachtray.

SUMMARY OF THE INVENTION It has now been discovered that the operationof a counter-current retort for oil shale can be improved by reducingthe refluxing and percolation in the bed. Local ized liquidaccumulations in the bed form carbonaceous agglomerates which wedge inthe air distribution assembly and burn in this hot oxidizing environmentto form clinkers that interfere with retort operability. Removal ofthese liquid accumulations from the shale bed reduces the formation ofcarbonaceous agglomerates and vitreous clinkers.

Localized liquid accumulations in the bed may be initiated by pieces ofrich oil shale or by locally high concentrations of fine shale in theshale bed. These fines are more heavily wet with oil by the impaction ofmist or by the surface condensation of oil than are large shale pieces.

As liquid is vaporized and cracked from these local accumulations, atarry, carbonaceous residue is left behind which binds pieces of shaleand dust together to form cohesive masses. This occurs at a temperatureof about 700 F. The cohesive masses of shale, dust, and tarry binder areconverted to dry hard agglomerates at temperatures between 800 F. and1200 F.

In accordance with the present invention, flooding is caused to occur ina controlled fashion at a section of the retort wherein liquid can bedisengaged. This reduces the likelihood of uncontrolled localized liquidaccumulations and thus breaks the chain leading to clinkering and retortinoperability.

BRIEF DESCRIPTION OF THE DRAWINGS Advantages of the invention willbecome apparent to those skilled in the art from the following detailedde scription considered in conjunction with the drawings wherein:

FIG. 1 is an isometric view cf a vertical shaft kiln type oil shaleretort, fitted with a liquid disengaging device constructed inaccordance with the present invention;

FIG. 2 is a sectional plan view showing two modules of the liquiddisengaging device illustrated in FIG. 1;

FIG. 3 is a sectional view of the liquid disengaging device on the line33 of FIG. 2;

FIG. 4 is an isometric view of a liquid disengaging device useful in thepractice of the present invention; and

FIG. 5 is a fragmentary sectional view that illustrates one method ofpositioning the liquid disengaging device of FIG. 4 within a shaleretort.

DESCRIPTION OF THE PREFERRED EMBODIMENT In the drawings, in so far aspossible, like part have been given the same reference number. Referringnow more particularly to FIG. 1, the basic apparatus of this inventionmay be appreciated. In general, the apparatus is an elongatedrectangular retorting vessel 10 lined with a heat resistant refractorymaterial 12. A charge hopper 13 is positioned at the top of the retort.The charge hopper may be of any suitable construction but should bedesigned to maintain a continuous feed of oil shale particles into thetop of the retort and at the same time maintain a gas seal to preservethe escape of gas and vapors from the retort through the chargingmechanism. As shown in the drawing, a rotary feeder 14 above the hopper13 provides a top gas seal and distributes oil shale in particulate formthrough the rotating chute 16 and feed pipes 18.

At the bottom of the retort, a discharging mechanism is providedconsisting of a diamond distributor 20, roll feeders 22 and screwconveyor 24. A second rotary feeder 25 provides a gas seal at the bottomof the vessel.

Extending horizontally from one wall of the retort are a plurality ofspaced header outlets 26 for recycle gas and directly thereabove arelocated a series of vertically opening distribution ports 28 foradmitting an oxygen containing gas such as air, into a combustion zone30.

An oil recovery deck plate 32 extends horizontally across the retortingvessel 10 and is sealed at its edges to a stainless steel liner 34. Theposition of this deck plate within the retort is important, as it shouldbe at such a level that retorting of the shale and some condensation ofhigh boiling fractions (without flooding) occur below the deck plate. Anoil disengager 36 extends above the deck plate 32 toward the preheatingzone and below the deck plate toward the combustion zone. The structureand operation of the disengager 36 will now be described with specificreference to FIGS. 2 and 3.

Each unit or module of the disengaging unit 36 is constructed withdownwardly diverging baffles 38 and 39 that extend completely across theretorting vessel from openings 40 in the deck plate 32. The length ofthe opening 40 is equal to the internal dimension of the retort; and thewidth of the opening is related to the shale particle size range and issufficient to establish the proper flow of shale through the retort.Upwardly diverging baffles 42 and 43 from openings 40 in the deck platealso extend completely across the retorting vessel. These baffles 42 and43 are constructed with lower longitudinal slots 44 and 45 in the wallsthereof. The slots 44 and 45 are positioned an equal distance above thedeck plate 32 and communicate therewith. Upper longitudinal slots 46'and 46 also communicate with the deck plate and are symmetricallypositioned in the walls of the baflles 42 and 43. As can be seen, theupwardly diverging baffles 42 and 43 of adjacent modules are capped byan inverted V shaped baffle having an apex 48 to form a deflector thateffectively prevents solid material from flowing onto the deck plate.Conduits 50 extending from the deck plate through the wall of the vesselprovide for the recovery of liquid products.

While the dimensions of the disengaging unit are not critical, the anglea should be at least about 50 to avoid the formation of a shale freesurface at which liquid could accumulate. Angle a should not be greaterthan 90". Increasing this angle above 50 within the range indicatedprovides improved operation of the disengaging unit at an increase inconstruction cost. The angle ,6 is less than 90 and may be as small as50 providing that the material passing through the retort will flow atthat angle; preferably the angle ,8 is between 70 and about 90 to insuresmooth shale flow with no inactive zone of shale between the opening 40and the upper longitudinal slots 46 and 46'. When the width of theopening 40 is about 14 inches, these conditions are achieved, and thegas flow through A to /2 inch shale with low liquid loading is about 3feet per second.

A disengaging system 51 useful in the practice of the present inventionis illustrated in FIG. 4. This device may be constructed of stainlesssteel with a longitudinal series of gas and oil inlet orifices 52separated by the surface 54 which functions as a shale chute from aparallel longitudinal series of gas outlet orifices 56. The disengagingdevice 51 is placed in the retorting vessel so as to prevent solidmaterial flowing downwardly through the retort from entering thesluiceway 58. The oil entering the inlet orifices 52 is separated fromthe associated gases and flows from the disengaging system at the oiloutlet 59. Another view of this device in a retort of the typeillustrated in FIG. 1 is shown in FIG. 5, wherein: inlet orifices areshown as 52, 52' and 52", the surfaces are shown as 54, 54' and 54", gasoutlet orifices are shown as 56, 56 and 56", and the sluiceways as 58and 58'.

The operation of the retort as shown in FIG. 1 will now be describedwith particular reference to the retorting of oil shale and inaccordance with a preferred embodiment of the invention. It is to beunderstood of course, that with or without modification, the processdescribed may be applied to the destructive distillation of otherhydrocarbonaceous solids, such as coal, lignite, peat, wood, etc., andthat many variations are possible within the scope of the invention.

Oil shale crushed to a suitable particle size, i.e. A to /2 inch, isintroduced into the top of the retort by means of hopper 13 and iscontinuously passed downwardly through the retort in an uninterruptedcolumn. The incoming oil shale from hopper 13 is at room temperature.The shale particle size can vary within relatively wide limits both asto maximum and minimum particle size and particle size distribution,depending on the size of the retort and the operating conditions.

The shale moves downwardly through the retort by gravity as a bed offreely moving particles and passes successively through asolids-preheating and product-cooling zone, a distillation zone, acombustion zone, and a residue cooling zone. The products of combustionand of distillation pass out of the top of the retort through the offgasheaders 19 and are conducted to the product recovery system.

A portion of the gas stream flowing from the headers 19 is withdrawn andrecycled to the retort through header outlets 26. The gas streamrecycled to the retort by header outlets 26 consists essentially of theflue gases resulting from combustion within the retort enriched bynoncondensible hydrocarbon gases produced by thermal decomposition ofthe kerogenous material in the shale. As used in the specification andin the claims, the term noncondensible gas refers to gases which fail tocondense to liquids at atmospheric temperatures and under ordinarypressures, including the light hydrocarbon gases (such as methane,ethane, propane, ethylene, propylene, etc.) produced during thedestructive distillation of the hydrocarbonaceous material, and the fluegases resulting from combustion including carbon dioxide, carbonmonoxide, and nitrogen.

This recycle gas, which is at a relatively low temperature (for example,to 200 F.) is introduced into the bottom of the retort by header outlets26 and flows upwardly through the downwardly flowing residue from thecombustion zone. In this portiton of the retort, herein termed theresidue cooling zone, direct heat exchange is effected between the coldrecycle gas and the hot residue; the cold recycle gas is preheated byrecovering sensible heat from the hot shale which in turn is cooled andleaves the retort at a temperature approximately that of the incomingcold recycle gas.

An oxygen-containing gas, preferably air, preheated if desired, isinjected into the combustion zone 30 through the distribution ports 28.The oxygen-containing gas is mixed with the preheated recycle gasesrising through the shale and is distributed in a uniform mannerthroughout the cross-section of the retort.

The ratio of recycle gas admitted at the bottom of the retort to the airadmitted into the combustion zone is an important variable since itdetermines other process variables such as the combustion zonetemperature. While the recycle gaszair ratio may vary within relativelywide limits, in general an excess of air should be avoided since thisleads to high combustion zone temperatures which in turn lead toexcessive mineral carbonate decomposition (which would absorb largequantities of heat). A deficiency of air leads to undesirably lowcombustion ZOne temperatures resulting in failure to fully retort theshale, causing lower yields and decreased throughput. Generallyspeaking, in the case of oil shale, under normal operating conditions,and employing the ordinary types of shale, recycle gas to air ratiosbetween about 2.5/1 and about 8/1 have been found to give the mostsatisfactory results. Using these ratios, moderate combustion zonetemperatures, between about l300 and about 1700 F. have been found togive the most satisfactory results.

The heat developed in the combustion zone is derived both from burningthe lean recycle gases and from burning some of the organic residueremaining on the shale descending from the distillation zone. Thisorganic residue is chiefly carbon in a reactive state which will burnvery readily.

Continuing to follow the gas and solids flow within the retort, the hotgas from the combustion zone rises countercurrently to the descendingshale thus effecting direct solids-to-gas heat exchange. The hot gasesgive up their heat to the shale rapidly bringing the shale to distillation temperatures, causing decomposition of the organic materialtherein, and evolution of oil vapors and noncondensible hydrocarbongases. These combustion and distillation products continue to risecounter-currently to the incoming cold shale and thus are cooled to thecondensation temperature below the deck plate 32 so that flooding occursat or immediately above the operating 40. As the shale descends betweenthe converging baflles 42 and 43 it passes through a relativelyquiescent isothermal region in which there is little gas flow. At theopenings 40 it is exposed to sufficient gas flow so that any liquidwhich is associated with the shale will not flow downwardly. The gasvelocity above the openings 40 conveys the condensed liquids upwardlyand laterally, normal to the gas flow through the longitudinal slots 44and 45. In the relatively low velocity shale free region 47 behind thebaffles 42 and 43, oil is disengaged from the gas and is drained offthrough the conduits 50. The associated gas which is now relatively freeof liquid is reinjected into the shale bed through the longitudinalslots 46 and 46, and goes overhead with the offgases for subsequentrecovery. While the retorting method described is applicable in generalto the destructive distillation of solid hydrocarbonaceous materials,including oil shale, coal, lignite, peat, wood, etc., it is particularlyadapted for the destructive distillation of oil shale. The term oilshale, as employed in the specification and claims, is intended to referto sedimentary rocks containing an organic material, usually termedkerogen, which upon heating yields a mixture of hydrocarbons and organicnitrogen, oxygen, and sulfur compounds, usually termed shale oil.Extensive deposits of oil shale are found in this country, particularlyin Colorado, Utah, and Wyoming, of which the deposits found in theso-called Green River shale formation are typical. The invention hasbeen found to be particularly applicable to the type of shale found inthe United States.

It is to be understood that the above description, together with thespecific examples and embodiments described, is intended merely toillustrate the invention, and that the invention is not to be limitedthereto, nor in any way except by the scope of the appended claims.

What is claimed is: 1. In a process for producing liquid hydrocarbonsfrom oil shale by passing a moving bed of said shale in particulate formdownwardly through a gas combustion retort and flowing the hot gas andvaporous products from the combustion zone thereof upwardly through theretort whereby a high boiling fraction of said vapors in condensed uponcontact with the counter-flowing shale; the improvement which comprises:

disengaging said high boiling fraction from the shale bed with hot gasby passage to an adjacent quiescent zone in the retort as the shalepasses through an area of high gas velocity above the combustion zone;

separating said high boiling fraction from entrained gases in saidadjacent quiescent zone which is a shale-free region of low gasvelocity, and

a high boiling liquid fraction; the improvement which.

comprises:

confining the gas and vapor stream as it moves upwardly through theretort toward the condensation zone to increase in velocity and proviedlateral movement of the high boiling liquid fraction into an adjacentshale-free region of low gas velocity wherein said liquid fraction isseparated from gases associated therewith, and returning the associatedgases from which liquid has been removed to the shale bed at a levelabout that at which said high boiling liquid fraction was removed. 3. Aprocess for the recovery of shale oil from oil shale which comprises:

initiating a zone of combustion in the lower portion of a downwardlymoving bed of oil shale in a gas combustion retort, flowing hotcombustion product gases upwardly through said downwardly moving bed ofshale whereby shale oil vapors are formed which undergo condensationupon contact with counter-flowing cooler shale particles in an upperportion of the gas combustion retort; disengaging from an upper portionof the moving bed of shale in a region of relatively high gas velocity amixture of noncondensible gas and liquid shale oil; separating thedisengaged liquid shale oil from noncondensible gas in a shale-free areawithin the retort, collecting the liquid shale oil, and returning thenoncondensible gas the the shale bed at a level above that at which theliquid shale oil was disengaged. 4. In a retorting apparatus forproducing shale oil from oil shale, the combination of:

an elongated vertical reaction vessel, means for introducing crushed oilshale to the interior of said reaction vessel, means for heating saidcrushed oil shale, and means within said reaction Vessel above theheating means for disengaging gas and liquid fractions from the oilshale and reengaging the gas with the shale at a higher level comprisingparallel and separated horizontal plates extending across said reactionvessel defining openings therebetween, downwardly converging bafl lesterminating in the openings between said plates and characterized byupper and lower longitudinal slots in the walls thereof, and divergingbafiles extending below said openings.

References Cited UNITED STATES PATENTS 2,723,225 11/1955 Elliott ,201-292,885,338 5/1959 Evans 208-11 CURTIS R. DAVIS, Primary Examiner U.S.C1.X.R.

